Research theme

Methanation system

This work is supported by JSPS KAKENHI Grant Number 20K12245


What does this technology aim to do?

This system is significant as a fuel producing system which doesn’t add to carbon dioxide emissions to the atmosphere

Fig.1 Methanation system

Methanation is a method which converts a mixture of carbon dioxide and hydrogen to methane. Methanation system employs a hydrogen generator, CO2 capture, methanation reactor and utilization equipment of CH4. It is a greenhouse gas reduction system that obtains electrode for electrolysis from renewable energy. In addition, by using surplus renewable energy, it will be able to equalize the demand gap.

What is biomethanation ?

It is methanation using methanogenesis.
We can get methane in mild condition; 37 degrees and at atmospheric pressure.

Fig.2 Biomethanation

In this study, Biogas from anaerobic digestion in wastewater treatment plant is targeted.

Fig.3 Biomethanation system in wastewater treatment plant


Subject of improvement

Goal: Miniaturization of reactor

Biomethanation reactor is about 100 times bigger in size than that in catalytic method

Problem: Hydrogen solubilization

Biomethanation has an advantage in reaction condition which is mild temperature 37degree. But its reactor size is over 100 times bigger than that in the catalytic method. To miniaturize the reactor, effective solubilization of hydrogen is important. Crude gases of biomethanation are carbon dioxide and hydrogen. The former is easily soluble in water, but the latter has 1/40 of its solubility. To accelerate bioconversion, hydrogen dissolution should be more effective.

Subject of improvement

Solution:Application of microbubble generator

Fig.5 Example for Biomethanation reactor employed microbubble generator

Surface area increases approximately 1000 times → Improved hydrogen diffusion  → Achievement of reactor miniaturization

To dissolve hydrogen effectively, diffuser selection is important. We propose a reactor implementing a microbubble generator, which produces smaller bubbles approximately 2 μm. These are 1000 times smaller than those produced by a conventional diffuser. It improves the diffusion of hydrogen so accelerating reaction efficiency and reaction time.